A compact cross-coupled dual-band bandpass filter based on folded Stepped Impedance Resonators (SIRs) with four controllable transmission zeros is proposed in this paper. A pair of stepped impedance tapped lines is utilized to improve the dual band impedance matching, which reduces the insertion loss of the filter; meanwhile the tapped lines are also coupled with non-adjacent resonators to produce transmission zeros to improve skirt characteristics. At the end of this paper, the simulated and measured results are compared with each other, and good agreement is achieved.

In this paper, we focus on the problem of optimizing plasmonic structures. A plasmon-assisted waveguide coupler is considered as a test problem, which leads to a five-dimensional optimization problem carried out by an evolution strategy (ES). The optimization results are verified by a comparative analysis between different solvers, i.e., the finite element package CONCEPTs and the multiple multipole program (MMP). We also compared with results obtained using a deterministic optimization algorithm, namely the Nedler-Mead method as implemented in the commercial software package COMSOL Multiphysics. Some issues concerning deterministic versus evolutionary optimization, in particular, in the field of plasmonics have been discussed.

We show that the combined use of radio frequency absorbers and directive antennas can produce significant changes of the radio propagation channel properties along the positions of a virtual array inside a reverberation chamber. A multidimensional characterization of the channel was performed at 40 antenna positions with spacing of 0.233λ at 1 GHz. The average power, the Ricean K-factor, the coherence bandwidth, the r.m.s. delay spread, the mean delay, the beamforming power angle spectrum and array antenna correlation have been studied for different arrangements in the reverberation chamber. The analysis shows that the joint average over time and frequency channel behavior is, as expected, rather homogeneous along the very large array. However, individual realizations of the channel present a pronounced selective behavior in space, time and frequency with parameters varying along the positions of the virtual array suggesting that a heterogeneous behavior of the radio channels can be emulated in reverberation chambers. An important application of the presented study comprises testing of antenna array designs and algorithms in multipath environments. Further development may lead to Over The Air testing of Multiple Input Multiple Output antenna systems of various sizes, i.e., from small to very large arrays.

A new family of metamaterial-inspired monopole antennas designed for GPS operation is reported. By adding a simple Split-Ring Resonator (SRR) into the near-field region of a monopole antenna resonating at 2.45 GHz, we have created a second resonance situated in the L1-band (f=1,537 for example) lower than the monopole's one. At this new resonance, the directivity of the structure was enhanced and its profile was reduced. Four SRR-configurations were considered depending on the orientation of the slot into the resonator. The structure was first optimized by adjusting the resonator size and the coupling distance between it and the monopole. Next, the directivity of the structure was improved by adjusting both the SRR-slot position and the coupling distance. Finally, the optimized structure in terms of size and directivity was realized and characterized.

The time-domain shielding effectiveness of planar conductive thin screens excited by a transient electric-line source is studied in detail by means of an approximate semi-analytical formulation based on a Cagniard-De Hoop approach. Such a formulation allows for easily deriving and discussing several definitions of time-domain shielding effectiveness, recently introduced in the literature. Comparisons with results obtained numerically through an exact canonical double inverse Fourier transform are provided which furnish a benchmark to discuss the advantages and limits of the proposed approximate formulation.

A compact dual-band MIMO antenna with high port isolation for WLAN applications is proposed. The proposed antenna is basically composed of two monopoles and designed at 2.4/5.2 GHz. High port isolation is achieved by introducing a T-shaped junction on the top surface of the substrate and etching two slots on the ground. The measured bandwidth of the proposed antenna are 2.34-2.55 GHz and 5.13-5.85 GHz, which are suitable for WLAN applications, and the measured isolation between the two monopoles is higher than 20 dB in both bands. Meanwhile, the envelope correlation coefficient of the antenna at both operating bands is lower than 0.001, which means that the antenna has high diversity gain. Good agreement is achieved between the predicted result and the measured data. The overall size of the proposed antenna is 38 mm×43 mm×1.6 mm.

Organic solar cells (OSCs) have recently attracted considerable research interest. For typical OSCs, it is highly desirable to have optically thick and physically thin thickness for strong light absorption and efficient carrier collection respectively. In the meantime, most organic semiconductors have short exciton diffusion length and low carrier mobility [1-3]. As a consequence, the active layers of OSCs are generally thin with a thickness of few hundred nanometers to ensure the efficient extraction of carriers, hence limiting the total absorption of incident light. Optimizing both the optical and electrical (i.e. multi-physical) properties of OSCs is in demands for rationally designed device architectures. Plasmonic nanomaterials (e.g. metallic nanoparticles [4-6], nanorods [7, 8], nanoprisms [9, 10], etc.) have recently been introduced into different layers of multilayered solar cells to achieve highly efficient light harvesting. The multilayered solar cells structures commonly have active layer, carrier (electron and hole) transport layer and electrode (anode and cathode). Through the localized plasmonic resonances (LPRs) [11-16] from metallic nanomaterials, very strong near-fields will be generated, which can provide a large potential for enhancing optical absorption in the multilayered OSCs. Besides the optical effects, it has been reported that metallic nanomaterials can modify the morphology, interface properties as well as the electrical properties of OSCs which will significantly modify the performances of OSCs [17-23]. In this article, the effects of various optical resonance mechanisms and the theoretical studies of the multi-physical properties of OSCs will be reviewed. Meanwhile, the experimental optical and electrical effects of metallic nanomaterials incorporated in different layers of OSCs will be studied. The morphology and interface effects of metallic nanomaterials in the carrier transport layers on the performances of OSCs will also be described.

The high-frequency method for the prediction of the terahertz (THz) radar cross section (RCS) of conductive targets with extremely electrically large size in free space was presented. In order to consider the scattering fields of the perfectly electric conducting (PEC) targets with extremely electrically large size in free space, the Green's function was introduced into the conventional physical optics (PO) method which was combined with the graphical electromagnetic computing (GRECO) method and improved using the partition display algorithm. The shadow regions were eliminated quickly by displaying lists of OpenGL to rebuild the targets, and the geometry information was attained by reading the color and depth of each pixel. The THz RCS of conductive targets can be exactly calculated in free space. The RCS comparison between the partition display GRECO prediction by the self-written Visual C++ 2010 program and the simulation of FEKO software with the large element PO method proves the validity and accuracy of the proposed method. The results provide an important basis and method for the potential applications of THz radar in many fields such as military, astronomy and remote sensing.

Research centers and industries often need to measure the microwave electromagnetic emission of hot bodies, in order to calculate their temperature. It is well known that the most critical part of a microwave radiometer is its receiver, to obtain a very sensitive system that can also measure low emissions this needs, among other features, to be very sensitive, necessitating the use of expensive low noise amplifiers. For some time now, low-cost components for the reception of satellite TV have been available on the consumer market. These are known as Low Noise Block (LNB), and they include, as a front-end, an amplifier with very low intrinsic noise. In this study, we wanted to test the feasibility of designing and using a 12 GHz total power radiometer, using, as a front-end, an LNB. The system was tested, in different configurations, to measure the emission due to natural sources (Earth, Sun and a sunny wall).

A new compact CPW-fed slot antenna for UWB applications is presented in this paper. The slot in the ground plane is asymmetric which helps in wide band impedance matching. The radiating element is a star-shaped geometry fed by a double stepped co-planar waveguide. Three antennas are designed with this geometry. Out of these three antennas, a compact antenna is proposed. The size of the proposed antenna is 27.2 x 32.2 mm², and it has a measured impedance bandwidth of 8.7 GHz (3-11.7 GHz). The radiation patterns are stable with respect to frequency and of bi-directional shape in E-plane and omnidirectional shape in H-plane. The measured and simulated results are in good agreement.

To extract the immunity model in an easy way and to complete the immunity simulation in a short time, it is preferred to consider only the disturbance propagation network in an integrated circuit system. However, through theoretical analyses, simulations and measurements, this paper shows that the on-chip transistor circuit has a nonuniform frequency response on its immunity against arrival disturbances. Including the nonuniform frequency response qualitatively improves the match between the simulation and measurement results. The conclusion is that both the disturbance propagation network and on-chip transistor circuit should be considered in the immunity simulation.

A novel microstrip antenna for triple-band WLAN/WiMAX applications is presented. Based on a face-shaped slot, the antenna consists of a pair of symmetrical eye-like patches, a smiling-mouth-shaped feeding line and a rectangular stub that looks like the fringe. The resonant mode at 3.5 GHz is excited by the basic radiation patch with the face-shaped slot. By adding a rectangular fringe-shaped stub on the top of the radiation patch and a pair of symmetrical eye-like patches without increasing the size of the antenna, the antenna can effectively generate three different resonances to cover the WLAN/WiMAX bands. The measured results show that the antenna has three separated impedance bandwidths for S₁₁<-10 dB of 550 MHz (2.36 GHz-2.91 GHz), 790 MHz (3.27 GHz-4.06 GHz) and 810 MHz (5.07 GHz-5.88 GHz), and the measured gain is above 2.8 dB over the operating band, which can be well applied for both 2.4/5.2/5.8 GHz WLAN bands and 2.5/3.5/5.5 GHz WiMAX bands.

Circularly polarized millimeter-wave travelling-wave antennas, using substrate integrated circuits (SICs) technology, are designed, fabricated and tested. By using the SICs technology, compact antennas with low losses in the feeding structure and with good design accuracy are obtained. The elementary antenna which is composed of two inclined slots is characterized by full-wave simulations. This characterization is used for the design and development of linear antenna arrays with above 16 dB gain and low side lobe level (<-25 dB), using di®erent power aperture distributions, namely uniform, Tchebychev and Taylor. Experimental results are presented at 77 GHz showing that the proposed antennas present good performances in terms of impedance matching, gain and axial ratio. These antennas have potential applications in integrated transceivers for communication and radar systems at millimeter-wave frequencies.

This paper proposes a method to estimate human exposure to electromagnetic field radiation in a variable and highly multiscale problem. The electromagnetic field is computed using a combination of two methods: a rigorous time domain and multiscale method, the DG-FDTD (Dual Grid Finite Difference Time Domain) and a fast substitution model based on the use of transfer functions. The association of these methods is applied to simulate a scenario involving an antenna placed on a vehicle and a human body model located around it. The purpose is to assess the electromagnetic field in the left eye of the human body model. It is shown that this combination permits to analyse many different positions in a fast and accurate way.

In this paper, indirect microwave holographic imaging of concealed ordnance is demonstrated. The proposed imaging technique differs from conventional microwave imaging methods in that it does not require the direct measurement of the complex field scattered from the imaged object but mathematically recovers it from intensity-only scalar microwave measurements. This brings the advantages of simplifying the hardware implementation and significantly reducing the cost of the imaging system. In order to demonstrate the ability of the proposed technique to reconstruct good quality images of concealed ordnance, indirect microwave holographic imaging of a metallic gun concealed in a pouch is carried out for airport security imaging applications. It is demonstrated that good resolution amplitude and phase images of concealed objects can be recovered when back-propagation is applied.

Previous invisibility cloaks were based on metamaterials, which are difficult for practical realization in visible light spectrum. Here we demonstrate a unidirectional invisibility cloak in visible light spectrum. By using water as the effective material and separated into several regions by glass sheets, a simplest and cheapest invisible device is realized. This device can hide macroscopic objects with large scale and is polarization insensitive. Owing to simple fabrication and easily acquisitive materials, our work can be widely applied in our daily life.

The contribution of electromagnetic wave scattering on density irregularities in the volume component of radar backscatter was analyzed for a thick snow pack containing internal hoar/ice layers. To evaluate the effect of this scattering, Density Deviation Factor (DDF), a statistical parameter, was introduced into the backscattering coefficient using the ``slice'' approach. DDF is proportional to the intensity of the density fluctuation and inverse to the mean density. The inverse dependence of backscatter with accumulation rate was discussed based on the DDF parameterization of snow inhomogeneities.

The paper presents a method of determination of ground fault current distribution when HV (high voltage) substations are located in urban or suburban areas, or where many relevant data necessary for determination of this distribution are uncertain or completely unknown. The problem appears as a consequence of the fact that many of urban metal installations are situated under the surface of the ground and cannot be visually determined or verified. On the basis of on-the-site measurements, the developed method enables compensating all deficiencies of the relevant data about metal installations involved with the fluctuating magnet field appearing around and along a feeding power line during an unbalanced fault. The presented analytical procedure is based on the fact that two measurable quantities, currents in one phase conductor and in one neutral line conductor, cumulatively involve the inductive effects of all, known and unknown surrounding metal installations. Once, this quantity has been determined, the problem of determination of different parts of a ground fault current becomes solvable by using a relatively simple calculation procedure. The presented quantitative analysis indicates at the benefits that can be obtained by taking into account the presence of surrounding metal installations.

A new ultra-wideband antenna with enhanced, nearly constant gain is presented. This quasi-planar antenna is composed of a CPW-fed printed monopole and a short horn, both made out of a single substrate. The measurements demonstrate an almost at peak gain of 5.5 dBi0.7 dB from 2.5 GHz to 15 GHz with the average gain difference in XZ plane is roughly 2 dB up to 8 GHz, which further rise to 6 dB at 10 GHz. The antenna also has a nearly linear phase response in this band. Well tested performance both in frequency and time domains, along with broad azimuth pattern, results in minimal ringing of a radiated pulse. The new antenna is suitable for establishing good line of sight link for UWB transmission and other broadband applications.

This paper presents a frequency and pattern reconfigurable stacked patch microstrip array antenna fed by aperture-coupled technique. The antenna consists of three substrate layers with radiating elements sorted at substrate layer 1 (top patches) and substrate layer 2 (bottom patches). The layers have different sizes to indicate different operating frequencies. On the ground plane, the four sets of two different aperture slot shapes (I-shaped and H-shaped) are used to transfer the wave and signal to particular radiating elements during the PIN diode switches configurations. The I-shaped slots are used to activate the bottom patches while the H-shaped slots are used to activate the top patches. Four PIN diode switches are placed at the feed line, positioned between the I- and H-shaped slots. Next, by changing the PIN diode switches configuration to ten cases, the proposed antenna has capabilities to change the operating frequencies and the pattern characteristics itself. The measured results of return loss, gain and radiation patterns are slightly shift compared to the simulated results.